Tips to Casting Clear Epoxy Resin
How do you successfully apply or cast clear epoxy resin? What is the secret to a nice, transparent resin without air bubbles, shrinkage, or yellowing ?
CHOOSE THE BEST EPOXY RESIN FOR YOUR PROJECT
With so many epoxy resins available, it is important to remember that not all of them are equal. And, most importantly, formulations cannot be used in every situation.
A specific epoxy should be chosen for each situation. Essentially, the first criteria is casting thickness.
If you are casting a large quantity of resin, you will need to be patient. You must use resins with a longer curing time. If the resin hardens too fast, you will lose any chance of observing shrinkage effects, yellowing, or waves at the surface of your resin.
By opting for a slower crosslinking time, you give your resin time to reach maximum hardness and to stay as smooth and as transparent as possible.
In summary, you have to make a choice: either casting in steps, with all the constraints and extra work that entails, or casting a larger mass and accepting that it will take more time to cure, with a controlled exotherm (the heat released by the chemical reaction between the resin and the hardener’s molecules).
CASTING YOUR EPOXY RESINS IN MULTIPLE STEPS
However, if you want to cast more than 2 inches, you will need to cast in several stages. In this case, it is imperative to wait for the first casting to have cooled to 22°C, otherwise the exotherm (the heat released by the chemical reaction between part A and part B), will accelerate the curing process of the second casting, which will certainly cause the undesirable effects of a poorly controlled exotherm.
Please note that when maximum casting thickness is indicated, they are for 1″ X 1″ X 1″ volumes.
MINIMIZE THE FORMATION OF BUBBLES IN THE RESIN
First of all, the thicker your resin is and the thicker it is cast, the more difficult it will be for it to get rid of its bubbles naturally. Resins with lower viscosity, similar to water, will get rid of bubbles more easily.
Furthermore, be aware that your mixing technique is also an important factor to control. It is therefore recommended to use a metal or plastic spatula, not a wooden stick or rod, and not a mixer that would incorporate even more bubbles.